Variable condenser



Nov. 9, 1937. A F SAAR 2,o98,597

VARIABLE CONDENSER Filed Aug. 4, 1934 222 a V %ai !NVENTOR FRAN SAARATTO R N EY Patented Nov. 9, 1937 UNITED STATES PATENT OFFICE VARIABLECONDENSEB Franz Saar, Berlin, Germany, assignor to TelefunkenGesellschaft fr Drahtlose Teleraplie m. b. II., Berlin, Germany, acorporatlon of Germany Application August 4, 1934-,-serlal No. ?38,458In Germany August 11, 1933 This invention relates to an improvedvariable condenser and more particularly to a rotatable condenser of thesolid dielectric type.

In the art of radio broadcasting it is desirable,

ing to the drive shat g can be accomplished, whereby the rotor plate ais fixedly secured to the shaft by means of a set screw h, while thestator plate b is not iastened to the shait but is fixedly maintainedrelative to the condenser casing k by means of a bent part i. The shaftg at the one end thereof is journaled on a ball in the casing, while theother end protrudes from necessary for reaching the final value oi' thecapacity, only at the places at which a layer is present.

FRANZ SAAR.

for reasons of saving space to have variable conthe casing and carriesat this place the drive disk 5 densers of possibly small dimensions. Inorder m. By means of a spring n, rotor and stator are to accomplishthis, in place of air condensers, pressed in intimate contact againsteach other. such having a solid dielectric for instance glass, Theconductive layers may obviously be of any mica, or hard paper are used.Due to the higher shape as is known for attaining definite effects.

10 constant of the dielectric the size of condensers Thus for obtainingthe entire variation at a ro- 10 for the same end Capacity could beconsiderably tation of 90 they may be formed of two diareduced. Duringthe operation many disadvanmetrically disposed quadrants. tages are thenfound to exist. Glass as the di- I claim: electric is readily fragile atthe required small 1. Variable condenser, in particular rotatable wallthicknesses. Mica has the disadvantage that condenser having twoconductive layers of dif- 15 it easily splinters and is relativelyquickly worn ferent polarity displaceable with respect to each ofi?. Theproduced mica powder easily causes other, characterized in that theconductive layers sticking" of the condenser. Hard paper causes areprovided on faces remote from each other of too meny losses., platesconsisting ot iron free magnesium silicate,

. In accordance with the invention it is therefore said plates glidingover each other in intimate 20 proposed to use as the dielectric ironfree magcontact. nesium silicate ntroduced into the art in recent 2.Condenser according to claim 1, charactertimes under the various names(Calit, Calan, ized in that the carriers for the conductive layerssteatite, etc.) Besides having low electrical losshave a reduced wallthickness necessary for reach-- 2 es and a high dielectric constantthese products ing the final value of the capacity, only at the have theadvantages of great hardness so that places at which a layer is present.the surface wearing is avoided, and they further- 3. A variablecondenser of the rotatable type more have a favorable property asregards work having two conductive layers of different polarity ingthem, so 'that it is possible to produce disks displaceable with respectto each other, characof 0,1 mm. thickness; By means of such thin terizedin that the conductive layers are provided 30 disks the capacity valuesof about 500/M.MF as on a portion of the faces remote from each otherordinarily required in the art of radio broadcastof plates consisting ofiron free magnesium siliing, can be attained by only two conductivelayers cate, said plates guided over each other in intiprovidedonsurfaces not facing each other of mate contact.

plates touching each other. 4. A variable condenser of the rotatabletype 35 An embodiment of the invention is shown by having two conductivelayers of difierent polarity way of example in the drawing. displaceablewith respect to each other, charac- Figure 1 shows a section through amounted terized in that the conductive layers are provided variablecondenser. on faces remote from each other of plates con- Figure 2 showsa top view of one of the two sisting of iron free magnesium silicate,the thick- 40 supports for the conductive layer. a. is the rotor, nessoi' said plates at the portion where said layers b the stator. Rotor andstator consist of disk are arranged-being such that the rotatable plateshaped round bodies of equal type and formed of is substantiallybalanced in all positions, said magnesium silicate. At the places c andd replates guided over each other in intimate concesses in the materialare in the surface of a halt tact. 45 circle so that at these places awall thickness of 5. A variable condenseof the rotatable type 0,1-0,2mm. is obtained. At the surface e thus having two conductive layers ofdifferent polarity produced (see Figure 2) the conductive layer isdisplaceable with respect to each other, characdisposed suitably byburring it into the di-electric terized in that the conductive layersare provided material. The-parts of the disk not covered by the on facesremote from each other of plates con- 50 conductive layer are likewiseprovided with resisting of nsulating material, said plates glidingcesses, but the wall thickness may here be left over each other inintimate contact. greater, so that the rotor plate is approximately 6. Avariable condenser according to claim 5 or completely balanoed. Inthecenter of the disk, characterized in that the carriers for the conhubs fare provided by means of which a fastenductive layers have a reducedwall thickness 55

